1. Field of the Invention
The present invention relates to a checking apparatus directed to as a test target a rod-like flavor-tasting article or a component thereof having an aggregate of a large number of small pieces, such as shredded leaf tobacco, to optically check the density of the small pieces. This checking apparatus can be used in, e.g., a system that manufactures a tobacco rod by wrapping shredded leaf tobacco with a wrapper, to feedback-control the amount of shredded leaf tobacco introduced to the tobacco rod and to eliminate a defective tobacco rod.
2. Description of the Related Art
In a process of manufacturing a flavor-tasting article such as a cigarette, tobacco rod, or tobacco filter, or a component of the same, to know whether the product is defective or not, the density of each constituent member of the flavor-tasting article must be checked. For example, in a system for manufacturing a tobacco rod by wrapping shredded leaf tobacco with a wrapper, an optical density checking apparatus is used to obtain the packed state of the shredded leaf tobacco in the tobacco rod. As a checking apparatus of this type, Jpn. Pat. Appln. KOKOKU Publication No. 8-2288 (corresponding to U.S. Pat. Nos. 4,805,641 and 4,986,285) discloses an apparatus for optically checking the density of a tobacco strand by using a light beam within a range of ultraviolet rays to infrared rays.
The present inventor checked the density of a tobacco rod by using a checking apparatus of the type disclosed in the above reference. The correlation between the light attenuation ratio and the weight of the shredded leaf tobacco was not accurately obtained depending on the characteristics of the shredded leaf tobacco in the tobacco rod. This problem may be posed because the following several important factors are not sufficiently considered.
First, the water contained in the shredded leaf tobacco largely influences the correlation between the light attenuation ratio and the weight of the shredded leaf tobacco. When the light-emitting element is an LED, the emitted light is not a single-wavelength light, but its wavelength band is wide, and accordingly the ratio of light attenuation caused by the shredded leaf tobacco changes depending on the wavelength. Because light is transmitted through the clearance of the packed shredded leaf tobacco or along the surface of the wrapper of the rod (which is influenced by circumferential change of the tobacco rod), the quantity of light coming incident on the light-receiving element is larger than that calculated considering the quantity of light actually attenuated by the shredded leaf tobacco. Furthermore, a measurement error occurs due to the dark current of the light-receiving element.
The present invention has been made in view of the problems of the prior art described above, and has as its object to provide a density checking apparatus which is directed to as a test target a rod-like flavor-tasting article or a component thereof having an aggregate of a large number of small pieces, such as shredded leaf tobacco, and which can optically check the density of the small pieces at high precision.
According to the first aspect of the present invention, there is provided an apparatus directed to as a test target a rod-like flavor-tasting article or a component thereof having an aggregate of a large number of small pieces, to optically check the density of the small pieces, comprising:
a first light source configured to emit a first light beam formed of light with a first wavelength not substantially transmitted through the small pieces;
a second light source configured to emit a second light beam formed of light with a second wavelength substantially transmitted through the small piece;
an optical system configured to synthesize the first and second light beams and to irradiate the test target with an obtained synthetic light beam;
a first measurement unit configured to measure first and second projected light quantities respectively corresponding to the first and second light beams included in the synthetic light beam before applied to the test target;
a second measurement unit configured to measure first and second reflected light quantities respectively corresponding to the first and second light beams included in the synthetic light beam reflected by a surface of the test target;
a third measurement unit configured to measure first and second passing light quantities respectively corresponding to the first and second light beams included in the synthetic light beam passing through the test target; and
an arithmetic circuit configured to calculate a transmitted light quantity of the second light beam transmitted through the small pieces on the basis of the first and second projected light quantities, first and second reflected light quantities, and first and second passing light quantities, and to calculate the density of the small pieces on the basis of the transmitted light quantity.
According to the second aspect of the present invention, in the apparatus according to the first aspect, the second measurement unit measures the first and second reflected light quantities by receiving and detecting both the first and second light beams included in the synthetic light beam reflected by the surface of the test target.
According to the third aspect of the present invention, in the apparatus according to the first aspect, the second measurement unit measures one of the first and second reflected light quantities by receiving and detecting one of the first and second light beams included in the synthetic light beam reflected by the surface of the test target, and measures the other one of the first and second reflected light quantities by calculation with a premise that the other one of the first and second reflected light quantities can be obtained with the same reflectance as that of one of the reflected light quantities.
According to the fourth aspect of the present invention, the apparatus according to any one of the first to third aspects further comprises a detection circuit configured to calculate a fluctuation value as a difference between a reference value representing the density of the small pieces and a measurement value of the density of the small pieces which is obtained by the arithmetic circuit, and a control circuit configured to control an amount of the small pieces to be introduced into the test target in a manufacturing system for the test target on the basis of the fluctuation value.
According to the fifth aspect of the present invention, the apparatus according to the fourth aspect further comprises an integrating circuit configured to calculate an average value of fluctuation values of a plurality of test targets obtained with the detection circuit and to transmit the average value to the control circuit.
According to the sixth aspect of the present invention, the apparatus according to the fourth or fifth aspect further comprises a comparative determination circuit configured to compare the fluctuation value and a threshold value and to determine whether the test target is defective or not.
According to the seventh aspect of the present invention, in the apparatus according to any one of the first to sixth aspects, the small pieces are shredded leaf tobacco, and the first and second wavelengths are 0.5 xcexcm to 0.8 xcexcm and 1.2 xcexcm to 1.4 xcexcm, respectively.
According to the eighth aspect of the present invention, in the apparatus according to any one of the first to seventh aspects, each of the first and second light beams comprises a laser light beam.
According to the ninth aspect of the present invention, in the apparatus according to the eighth aspect, at least one of the first to third measurement units has a composite light-receiving element configured to receive and detect the first and second light beams on one optical path.
According to the 10th aspect of the present invention, in the apparatus according to any one of the first to ninth aspects, the synthetic light beam applied from the optical system to the test target comprises a parallel light beam.
According to the 11th aspect of the present invention, in the apparatus according to any one of the first to 10th aspects, the first measurement unit measures the first and second projected light quantities by receiving and detecting the first and second light beams included in a beam portion separated from the synthetic light beam between the optical system and the test target.
According to the 12th aspect of the present invention, the apparatus according to any one of the first to 11th aspect further comprises a mirror, which is disposed between the optical system and the test target, and has a mirror surface facing the test target to be inclined with respect thereto and a hole matching with an optical axis of the optical system, wherein the synthetic light beam from the optical system passes through the hole as a convergent light beam with a focal point falling on the hole and is thereafter applied to the test target, and the synthetic light beam reflected by the surface of the test target is reflected by the mirror and is introduced to the second measurement unit.
The embodiments of the present invention include inventions at various stages, and various types of inventions can be extracted from appropriate combinations of a plurality of disclosed constituent elements. For example, when an invention is extracted by omitting several ones from all constituent elements shown in the embodiments, to practice the extracted invention, the omitted portions are compensated for by known conventional technique.
According to the present invention, in an optical density checking apparatus directed to as a test target a rod-like flavor-tasting article or a component thereof having an aggregate of a large number of small pieces, such as shredded leaf tobacco, when the first light beam not substantially transmitted through the small pieces and the second light beam substantially transmitted through the small pieces are used, the density of the small pieces can be checked at high precision.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.